1. Field of the Invention
The present invention relates to a display tube that can emit light partially and a display device constituted by combining a plurality of display tubes.
There is a limit on increasing a screen size of a single display. Therefore, a large display of an array format in which multiple display tubes are arranged has been developed toward commercialization.
2. Description of the Prior Art
A large display utilizing the light emission principle of a surface discharge type plasma display panel (PDP) is disclosed in Japanese unexamined patent publication No. 2000-315460. The display device shown in FIGS. 15 and 17 in the document includes multiple display tubes arranged in parallel and a substrate for supporting the display tubes. Each of the display tubes includes strap-like display electrodes arranged on the outer surface of a glass tube containing a discharge gas in the length direction, and elongated address electrodes (data electrodes) arranged in the glass tube so as to cross all the display electrodes. Two display electrodes neighboring at a predetermined gap constitute an electrode pair for surface discharge. On the substrate, band-like bus electrodes (power supplying conductors) are arranged so as to cross the data electrodes, and the display tubes are disposed on the substrate so that the display electrodes contact the bus electrodes. The bus electrode makes electric connection of the display electrodes at the same position in the length direction of all the display tubes. In other words, the bus electrodes and the data electrodes form an electrode matrix. In the same manner as a single PDP, a potential control of the electrode matrix is performed for displaying a desired image.
Since the display electrodes are formed in each of the display tubes, it is easy to determine the area (i.e., the position of cells) that generates surface discharge, compared with a structure in which a bus electrode for plural display tubes is used as the display electrode.
As explained above, the form of arranging strap-like display electrodes for generating surface discharge along the length direction is suitable for reducing a diameter (a width) of display tubes, compared with a form of arranging a pair of elongated display electrodes along the length direction for generating surface discharge along the width direction. It may impair the productivity to classify colors of fluorescent materials in a display tube for a color display. Therefore, if one display tube has one light emission color, three display tubes consist a pixel. It is desirable for a high definition color display to thin the display tube for reducing a cell pitch in the tube arrangement direction.
In the conventional device, display electrodes making a pair are arranged closely to each other for forming a small surface discharge gap, so that a driving voltage can be lower than in the case of opposing discharge that traverse a tubular discharge space in the radial direction.
The conventional display device has a problem that though discharge can be generated at lower voltage than in the opposing discharge type by reducing the gap between the display electrodes, it is difficult to improve light emission efficiency.
An object of the present invention is to improve light emission efficiency without raising a breakdown voltage.
According to the present invention, a display tube having a tubular vessel defining a discharge gas space is used for a display, and a pair of display electrodes generates surface discharge along the circumferential surface of the vessel and opposing discharge traversing the inside of the vessel. A breakdown voltage can be lowered by shortening a surface discharge gap, and a positive column having high excitation efficiency can be extended by generating opposing discharge at a portion where the electrodes are opposed to each other at a distance similar to a diameter of the vessel. The display tube has a display electrode pair having portions being close to each other along the circumferential surface of the vessel and portions opposed to each other with respect to the discharge gas space, so that the surface discharge transfers to the opposing discharge.